Rock drills are frequently guided by feed shells which have a feed guide for directing the rock drill. Feed guides are often times fabricated from aluminum to reduce the weight of the feed shell which also serves to improve the strength/weight ratio. An adapter plate onto which the rock drill mounts is fitted with gibs which slidably engage guiding surfaces of the feed guide. The sliding contact can result in excessive wear of the gibs and guide surfaces, particularly when operating in a drilling environment laden with rock fragments.
Rock drilling, by its very nature, produces rock fragments, while drilling a hole, which need to be flushed from the hole as the drill advances. When a liquid is used to flush the holes being drilled, the operating environment of the feed shell remains reasonably friendly. However, when the flushing fluid is air rather than a liquid, the environment becomes hostile and the service life of the guiding surfaces of the feed guide is substantially reduced from the life which can be obtained when liquids are used as the flushing agent.
When drilling a rock substrate such as limestone, the operating life for the guide surfaces of the feed guide can be as short as four (4) months when air flushing is employed. Thereafter, the feed guide needs replacing. Thus, there is a need for an improved feed shell for mounting air flushing drills which extends the operating time before service or rebuilding of the feed shell is required.